The basics:
Average salary should be anywhere between 200,000-250,000 yen/month.
Visa: Working holiday/ proper visa depending on length of assignment
Tips: It's easier to get a job if you're already there. So, you might consider taking a vacation in Japan first, and browsing the classifieds once you're there. Might also help you get acquainted with the people and culture. the Japanese are very polite, tradional and the girls are really beautiful.
If you're getting a job in Tokyo, make sure the employer provides you with just about everything you need. It's prohibitively costly to do things on your own, specially if it's all new to you.